Question: How long should an average chapter be?
There are no hard and fast rules regarding the length of chapters, but there are some guidelines you might consider.
1. Audience. If you're writing a children's book, your chapters should be shorter because long chapters look daunting to children, especially if they are not strong readers. You might take a look at some great books by different authors in your genre and see if your audience tends to favour chapters of a certain length.
2. Pacing. Ideally, a chapter should be long enough to not make the story seem choppy, yet short enough that a person can say to themselves, "Oh, maybe I'll just read the next chapter before bed." In other words, something that an average reader could comfortably read in 10-30 minutes.
3. Variety. Chapters don't have to be all the same length, and a little variety never hurts. Very important chapters may be longer. Chapters that present a single plot point may be short.
4. Structure. Ideally, a chapter will contain one or more events, take the reader on an arc (so the chapter ends with the story in a different emotional/intellectual place than where it started), and end at a point where you have made the reader curious about what will happen next - so they'll want to keep reading. Sometimes you can do this in a short space. Other times, you need more room.
5. Point of view. Ideally, each chapter should be written from the point of view of one character. If you want to switch points of view, it's best to do so at a chapter break.
6. Scene. It is often helpful (but not required) to include a chapter break when you shift time, as in the start of a flashback or flashforward, or when you jump to a different location.